Electric personal care devices, such as electric toothbrushes, are a growing market, and produced by a large number of manufacturers. While these personal care devices may vary in their operations, most contain an electric motor adapted to rotate a brush head in a reciprocating axial and/or tangential motion.
In operation, the electric motor in these personal care devices may be subjected to varied unwanted, unintended and/or otherwise detrimental reactionary forces. These forces can impact the effectiveness of the personal care devices, and can negatively impact a user's experience with the device. For example, an electric toothbrush may be subjected to a detrimental reactionary force that arises from friction between the user's teeth and rotating bristles of the brush head of an electric toothbrush, as the bristles reciprocate back and forth across the user's teeth. As another example, if the center of mass of the brush head is misaligned with the axis of rotation of the electric toothbrush device, an unwanted reactionary force may arise from drive motion of the motor on the brush. These detrimental forces can manifest as tangential reciprocating loads on the electric motor disposed within the electric toothbrush.
These forces are considered detrimental as they may cause unwanted behavior from the electric motor. For example, most electric motors have a shaft or spindle that rotates. The shaft is mounted in the bearings within the electric motor. If there is any clearance between the bearings and the shaft of the electric motor, these detrimental forces could cause the shaft come off the surface of the bearings and then impact the bearings, resulting in an unpleasant rattle and unnecessary wear on the shaft and bearings.
Accordingly, there is a need in the art for an electric motor that will not rattle or experience unnecessary wear due to these detrimental forces.